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Asked: 2026-06-14T22:32:36+00:00

I have an input timestamp from C# ( .NET epoch: 00:00:00 (midnight), January 1,

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I have an input timestamp from C# (.NET epoch: 00:00:00 (midnight), January 1, 0001) and I want to output it in Ruby world (Unix epoch: 00:00:00 UTC on 1 January 1970).

The input timestamp is given in UTC, and derived from .NET’s DateTime(Int64), which is “a date and time expressed in the number of 100-nanosecond intervals that have elapsed since January 1, 0001 at 00:00:00.000 in the Gregorian calendar.“

The input timestamp: 634891434586852680

Output should be 2012-NOV-21 a bit after 5pm PST.

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  1. Editorial Team
    input =                         634891434586852680
UNIX_EPOCH_IN_100NS_INTERVALS = 621355968000000000

Time.at((input-UNIX_EPOCH_IN_100NS_INTERVALS)*1e-7).utc.getlocal
 => 2012-11-21 17:10:58 -0800

    In Ruby, Time is stored internally as the number of seconds with fraction since the Epoch, January 1, 1970 00:00 UTC. Therefore we must convert from 100-nanosecond intervals to seconds.

    The conversion factor of 1e-7 is 1e2/1e9 which is 100/1000000000 which can be explained as:

    X intervals * 100ns/interval * 1s/1000000000ns

    The intervals cancel themselves out, as do the nanoseconds, and we are left with seconds; and 100/1000000000 seconds is 1e2/1e9 seconds which is 1e-7 seconds.

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